You of all people should understand BSFC differences between RB turbos and ST setups.

RBs don't have anything to do with this.
The turbo hardware induced BSFC difference is minor. What is needed for power is octane by meth or ethanol. Selecting meth means the fuel system upgrade is not needed, especially if a proper flash, such as Procedeflash is applied. The upgrade is needed running 100% e85 without meth.